Vacuum vessel



Dec. 22, 1942 E. GREIFENDORF VACUUM VESSELS Filed 001:. 25, 1940 Y FIGS.

llll llllllllllllllIlIlHllllIlv E/FMNGfi/A'FE/VDORF INVENTOR iatented Dec. 22, 1942 VACUUM VESSEL Erwin Greifendorf, Berlin, Germany; vested in the Alien Property Custodian Application October 23, 1940, Serial No. 362,463

In G

4 Claims.

This invention is concerned with the exhaust tube of electron tubes or other vacuum vessels, that is, the tubular extension thereof where a pump is connected for evacuating them. The practice has been so to seal off this exhaust tube that there remains a closed nozzle projecting from the vacuum vessel. This nozzle is liable to injury, thus endangering the vacuum, and besides is unnecessarily in the way when such electron tubes are to be removed and replaced in compactly designed apparatus.

Arrangements are known in which the said nozzle is provided with a protective covering of metal, press board or other suitable material. Also, a handle for removing the electron tube may be detachably fitted to such covering. These arrangements, however, involve a great expenditure in space and material.

According to the invention described hereafter the exhaust tube is sealed off in such a manner that the material of which it consists is incorporated in the wall of the vacuum vessel, any nozzle or other projection of the bulb thereof being removed in this way. To such end a special moulding device is used in the manufacture of the vacuum vessel, as will be understood from the following description and the accompanying drawing. In this drawing, Fig. 1 is a sectional view which shows a constructional form of the said moulding device and also illustrates a step of the method of manufacturing bulbs as provided by the invention. Fig. 2 is a sectional view representing another step of this method. Fig. 3 is a fragmentary sectional view of a bulb as produced by means of the moulding device. Fig. 4 is a sectional view showing a modification of the device represented in Figs. 1 and 2. Fig. 5 is a fragmentary sectional view of a finished bulb manufactured in accordance with Figs. 1 to 3. Fig. 6 is a fragmentary sectional view of a bulb manufactured by means of the device shown in Fig. 41. Fig. '7 is a detail view of a member that forms part of the device represented in Fig. 4 and which after the manufacture of the bulb, Fig. 6, forms part of this bulb.

The moulding device shown in Figs. 1 and 2 comprises a lower die 2 and an upper die 3. Over die 2 a piece of glass tube l is inserted as illustrated in Fig. 1. From this tube the bulb illustrated in Fig. 5 is manufactured. To such end the glass tube I has a suitable part thereof projecting beyond die 2. This part is heated, for instance by gas jets, as indicated in dotted lines, and is in this way melted down onto die 2, as illustrated by arrows and the dotted line position ermany November 20, 1939 of the softened part of tube I. The glass on die 2 is then moulded with the aid of die 3, as will be understood from the Fig. 2. The dies are so shaped as to produce the glass structure I, 4, l, Figs. 2 and 3, that is, a bulb having an exhaust tube 4' which forms an exhaust opening 5 shaped as shown in Fig. 3. This opening is reduced where it joins the interior -of the bulb I,'4 so that a cavity or depression is formed within the vitreous material 4. Tube 4' is now heated, as by the gas jet indicated in dotted lines. The Vacuum within the bulb acts to draw the softening material of the tube 4' into such depression, as.

indicated by arrows, and with an appropriately calculated height of sealing off the tube 4' this depression will be filled up without any projection forming on the outer surface of the bulb. In this way the lens-shaped wall portion 4 shown in Fig. 5 is produced at the top of the bulb. It will. be seen, however, that the top of the bulb may be other than lens-shaped. In any case it should be thick enough to prevent the heat acting on the tube 4 from deforming the inner surface of wall portion 4.

In Figs. 4, 6 and 7, 6 denotes a metallic sleeve carried by the upper die 3' and secured to it by frictional contact. This sleeve has a flange which by. the moulding process is in part embedded in the vitreous material, as shown in Fig. 6 and hence is stripped oil from die 3 when this is withdrawn from the bulb. Sleeve 6 is calculated to be flush with the outer surface of wall portion land with the vitreous material 4" with which it is filled by melting the exhaust tube, that is, the tubular extension equivalent to the tube 4, Figs. 2 and 3.

. As will be seen in Fig. 6 a handle, not represented, may be inserted over the sleeve 6 and be fastened to it by means of a screw joint or a, bayonet joint. Fig. '7 shows the sleeve to be provided with screw thread 8 to such end. In order to prevent the sleeve from turning when attaching the handle to it, its flange may be milled or serrated, as illustrated in Fig. 7 at I. With the aid of such a handle electron tubes whose bulb is of the novel construction may be exchanged through an aperture in the wall of an apparatus of which they form part.

What is claimed is:

1. In the manufacture of glass bulbs for vacuum vessels the method which comprises forming the glass bulb with an exhaust tube having a depression communicating with the interior of the bulb, and thereafter closing said depression with vitreous material obtained from the exhaust tube by melting said tube down into the depression.

2. In the manufacture of glass bulbs for vacuum vessels the method which comprises forming the bulb with a thickened wall portion and an exhaust tube projecting therefrom, said wall portion having a depression communicating with the exhaust tube and with the interior of the bulb, and thereafter closing said depression with vitremelting said tube down into the depression.

3. A glass bulb having a thickened wall portion and a. vitreous exhaust tube formed integral therewith, this wall portion having a depression ous material obtained from the exhaust tube by 10 ERWIN GREIFENDORF. 

